Abstract: It has been determined that the symmetric stretching frequency of water at concentrations of 10 ppm and more in liquid hydrocarbons is effectively independent of the nature of the hydrocarbon. On this basis one can rapidly, accurately, and precisely measure such water concentrations by comparing the transmittance of a narrow band of infrared frequencies within the symmetric stretching band of a wet sample with the transmittance at a frequency in the 3770-4000 cm.sup.-1 range, performing a second comparison with a dried sample, and forming the ratio of the two comparative measurements as a measure of dissolved water content.